1. Field of the Invention
The present invention relates to a compressible fitting for the fabrication of a permanent, tight connection between tubes.
2. Background Information
Compression fittings made of carbon steel or high-alloy steel, for interior installation, are known in the prior art. A brochure published by Mannesmann Edelstahlrohr GmbH shows such a fitting. The core of this system is a deformable compression fitting fabricated from a section of tube which, depending on whether it is designed as an elbow, tee or reducer, has at least one end that is hook-shaped and bead-like and holds a gasket. Adjacent to this end is a cylindrical area extending in the longitudinal direction. Attached to the end of the extension of this cylindrical area is a bead-shaped recess which extends radially inward and serves as a stop for the flat-ended tube that can be inserted. By means of an activation apparatus that is connected with a locating device having hinged jaws, the bead-like end is plastically deformed and the enclosed gasket is elastically deformed.
In addition, with the same compression process in the cylindrical area of the fitting, in the immediate vicinity of the bead-like end, a bead-shaped recess is pressed and the tube inserted underneath it is compressed along with it. The elastically deformed gasket in this connection system performs the sealing function, while the compressed bead-shaped recess absorbs the longitudinal forces produced by the internal pressure.
A disadvantage of this system is that on account of the high requirements regarding surface quality and dimensional tolerances, the compression fitting is fabricated from a section of a specially manufactured tube, using several deformation and transformation steps. The basic, or initial, tube is usually a seamless or longitudinally-welded tube that is subjected to a heat treatment following cold deformation. This specially manufactured tube requires close tolerances and a high surface quality. To manufacture a compression fitting from this tube, the original tube is cut into sections and the desired final cross section shape is produced by performing several transformation steps, e.g. tapering, crimping and chasing. Since the basic product, or raw material, is already relatively expensive, the compression fitting manufactured from it is also relatively expensive.